To find the damage, I decided I should measure the trunk lid carefully.
Here I've put it up on my 4' x 4' table. The tape along each edge is marked every inch from the back to the front. It is just over 51 inches long. I put cabinet shims at the corners to get them an equal height up from the table surface.
Here I am measuring, at each inch mark, the height from the table to the surface of the metal. Each measurement, and the mark at which it was taken, is written down; over 100 data points in all. Now a table of numbers is not very easy to see the trends, so I put the data in a spread sheet, and printed a graph. Now it is obvious where the damage is:
The horizontal axis is inches, with 0 at the back (near the windshield), and 50 at the front of the car. The vertical axis is in 1/1,000 of an inch, so "500" means 0.500 inch, "1000" is 1.000 inch, and so on. Clearly the right is bent up almost 1/2 inch compared to the left.
Now, being an engineer, I wanted to use a precise method to straighten the trunk lid. So ... I got up on the table, put my foot on the high spot, and stood my weight on it until I felt it "give". I was really afraid that I had made matters worse, but I shimmed the corners and took the measurements again:
Wow. Got it perfect on the first try. I actually put the trunk lid back on the car just to prove I wasn't fooling myself. Fit great! Declare victory and move on!